Answers: Choice A and Choice C
Step-by-step explanation:
Think of the vertical lines as train tracks (the metal rails).
Stuff between the rails are interior angles.
Angles 3 and 6 are one pair of alternate interior angles because they are on alternating sides of the transversal line. The other pair of alternate interior angles are angles 4 and 5.
Alternate interior angles are congruent when we have parallel lines like this.